Small-sized motor and manufacturing method thereof

ABSTRACT

In the case of a small-sized motor of the present invention, a printed board to which an electric circuit including an electric element is attached is mounted on a case cover. The printed board has a soldering part to be connected to a member attached to an interior of the case cover for being connected to an electric power source supplied from an outside and a soldering part to be connected to a projection in a notch provided on an opening part side of the metal case to body-earth the electric circuit. In the soldering part for the body-earthing, at the time of assembling the motor, after fitting the case cover to the metal case opening part, a pair of electrodes are brought into contact from an outside of the metal case near the soldering part, to weld the soldering part by a principle of the electric resistance welding. Consequently, it is possible to easily and surely body-earth the earth of the electric circuit to the metal case, and to reduce the number of the motor assembling steps so that the assembling can be performed with a good working property.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a small-sized motor, and moreparticularly relates to a small-sized motor wherein an electric elementsuch as a capacitor is attached to a case cover for being used for thedriving of electrical equipment or the like.

[0003] 2. Description of the Related Art

[0004] A small-sized motor is widely used in a vehicle electricalapparatus such as a vehicle door lock opening and closing device, anelectrically powered mirror mirror-surface driving and containingdevice, or an air conditioner. In the case of the small-sized motor andthe peripheral equipment like this, the reduction of electric noisecaused at the time of operation is required, and regulations are laiddown all over the world. CISPR25 as an international standard,GMW3100/3097 as a carmaker standard, or the like can be mentioned.

[0005] In order to reduce the electric noise, in the case of asmall-sized motor, it is necessary to directly attach the electricelement such as a capacitor or a choke coil to the motor. Therefore,conventionally, it has been performed that the electric element isarranged and wired on a printed board, and that this printed board ismounted on the motor. However, in the case of a mounting method likethis, such a work is necessary, where a special earth lead wire forearthing the electric circuit is connected to the printed board inadvance, and furthermore, this printed board is mounted on a metal caseof the motor, and after that, the above described earth lead wire isconnected, for example, by soldering.

[0006] In order to reduce the man-hour of such a troublesome work, aprinted board mounting method as shown in FIG. 6 is conventionally wellknown (refer to Japanese Utility Model Publication No. 63-127254). InFIG. 6, a printed board 25 to which an electric element (omitted in thedrawing) is attached is structured such that it is mounted to a metalcase 1 where the motor main body (omitted in the drawing) is contained,and after that, furthermore, it is covered by a case cover (omitted inthe drawing).

[0007] As shown in the drawing, to the metal case 1, a projecting needlepart 26 projected from an opening end edge is provided, and in themeantime, corresponding to this projecting needle part 26, to theprinted board 25, an engaging part 28 which makes the projecting needlepart 26 pass to an earth electrode part 27 is provided. As shown in thedrawing by an alternate long and short dash line and an arrow, in orderto make the state where the projecting needle part 26 is inserted intothe engaging part 28, the printed board 25 is mounted on the metal case1, and after that, by performing the soldering of the projecting needlepart 26 and the earth electrode part 27, the earth electrode part 27 ofthe printed board 25 and the metal case 1 are electrically connectedthrough the solder.

[0008] Thus, it is enough for the purpose only to perform the solderingon the way of the motor assembling step, and therefore, it becomespossible to largely reduce the working man-hour in the earth executingstep. However, in the case of such a prior art, the soldering is stillneeded as another step different from the motor assembling, andtherefore, the reduction of the working man-hour is furthermorerequired. Furthermore, it is required to attach the electric element tothe synthetic resin case cover with a good workability to efficientlyattach it in a narrow space.

SUMMARY OF THE INVENTION

[0009] Therefore, it is an object of the present invention to solve suchproblems, and to perform the assembling with a good workability in sucha way where an electric circuit composed of an electric element such asa chip capacitor attached on a printed board is attached to a casecover, and in the meantime, the earth of the electric circuit is easilyand surely body-earthed to the metal case, and the number of the motorassembling steps is reduced.

[0010] The small-sized motor of the present invention includes: a hollowcylindrical metal case with a bottom where a magnet is attached to aninside periphery; a synthetic resin case cover which is fitted to closean opening part of the above described case; and a rotor where alaminated core, a winding wound around the above described laminatedcore, and a commutator are attached on a shaft. To this case cover, aprinted board where an electric circuit including an electric element isattached is mounted. The printed board has a soldering part which isconnected to a member attached to the interior of the case cover forbeing connected to an electric power source supplied from the outsideand a soldering part which is connected to a projection in a notchprovided on the opening part side of the above described metal case forbody-earthing the earth of the electric circuit. In the soldering partfor the body-earthing, at the time of assembling the motor, a pair ofelectrodes are brought into contact from the outside of the metal casenear the above described soldering part to weld the above describedsoldering part by the principle of electric resistance welding, afterfitting the case cover to the metal case opening part.

[0011] In the case of the manufacturing method of a small-sized motor ofthe present invention, after inserting a rotor where a laminated core, awinding wound around the above described laminated core, and acommutator are attached on a shaft, into a hollow cylindrical metal casewith a bottom where a magnet is attached to an inside periphery, asynthetic resin case cover is fitted to close an opening part of theabove described case. To the case cover, a printed board where anelectric circuit including an electric element is attached is mounted.The printed board has a soldering part which is connected to a memberattached to the interior of the case cover for being connected to anelectric power source supplied from the outside and a soldering partwhich is connected to a projection in a notch provided on the openingpart side of the above described metal case for body-earthing the earthof the electric circuit. At the time of assembling the motor, afterfitting the above described case cover to the metal case opening part, apair of electrodes are brought into contact from the outside of themetal case near the soldering part for the body-earthing so that theabove described soldering part may be welded by the principle ofelectric resistance welding.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a vertical cross sectional view showing a total of asmall-sized motor to which the present invention can be applied by anupper half cross section;

[0013]FIG. 2 exemplifies a typical electric circuit used for a reductionof noise;

[0014]FIG. 3 is a view showing only a case cover of a small-sized motorshown in FIG. 1, and FIG. 3A is a view of an interior seen from aninside direction of the case cover, and FIG. 3B is a cross sectionalview made by cutting the case cover shown in FIG. 3A at the center;

[0015]FIG. 4 is a view showing a metal case, and FIG. 4D is a view madeby seeing an interior from an opening part of the metal case, and a viewmade by seeing this view from an upper side is FIG. 4A, and a view shownby an upper half cross section seen from the side is FIG. 4C. FIG. 4B isa view showing an expanded projection 10 provided on the opening partside of the metal case;

[0016]FIG. 5 is a view exemplifying a printed board; and

[0017]FIG. 6 is a view for explaining a printed board mounting methodbased on the prior art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018]FIG. 1 is a vertical cross sectional view showing a total of asmall-sized motor to which the present invention can be applied by anupper half cross section. To an inside periphery of a case 1 formed likea hollow cylinder with a bottom by a metal material, a magnet 2 (referto FIG. 4D) is attached. To an opening part of this case 1, a syntheticresin case cover 11 is fitted, and the opening part is closed by thecase cover 11. In a center of the case cover 11, a bearing 3 for a shaft21 is contained.

[0019] The other end of the shaft 21 is supported by a bearing 3provided at a center of the bottom part of the hollow cylindrical case 1with a bottom. To this shaft 21, a laminated core 22, a winding 23 woundon the above described core 22, and a commutator 24 are usually providedto compose a rotor of a small-sized motor. Then, each of a pair ofcarbon brushes coming into contact with this commutator 24 is attachedto the brush device fixed to the case cover 11.

[0020]FIG. 3 is a view showing only a case cover of a small-sized motorshown in FIG. 1. FIG. 3A is a view of an interior seen from an insidedirection of the case cover, and FIG. 3B is a cross sectional view madeby cutting the case cover shown in FIG. 3A at the center. As shown inthe drawing, the brush device is made of a pair of carbon brushes 4coming into sliding contact with the commutator, brush arms 5 where theyare respectively pressed and held, and brush bases 6, 7 connected tothese brush arms 5 by caulking or the like.

[0021] In the synthetic resin case cover 11, the brush device structuredlike this is pressed and held in the concave place limited by thecolumned part integrally formed with that. The electric power sourcesupply to this brush device is performed through a pair of brush springs8 functioning as the receptacle terminals coming into electric contactwith a pair of external terminals inserted from the outside through theexternal terminal inserting holes. At that moment, one brush spring isconnected to the brush base 6 electrically directly, and the other brushspring is connected to the brush base 7 in series through the choke coil16.

[0022] The above described attachment configuration of the brush deviceand electric power source supply configuration thereto can be made by aconventionally well known normal technique. The present invention ischaracterized by such a structure where to the case cover of asmall-sized motor to which a brush device like this is attached, aprinted board 12 to which an electric circuit element for the reductionof noise is attached is furthermore mounted, and in the meantime, theearth of this electric circuit is body-earthed to the metal case.

[0023] In FIG. 2, a typical electric circuit used for the reduction ofnoise is exemplified. Three circuits shown in (A) to (C) themselves arewell known, but which circuit should be used (or whether another circuitshould furthermore be used) is determined by the target value of howmuch the electric noise should be reduced. A choke coil L of the circuitelement shown in the drawing can directly be attached to the case coveras mentioned above (refer to the choke coil 16 shown in FIG. 3(A)). Chipcapacitors C1 to C3 except for the choke coil L and the winding thereofare put into practice by using the printed circuit.

[0024]FIG. 5 is a view exemplifying the printed board. In the case ofthe exemplified printed board, in order to make the circuit shown inFIG. 2A, as an electric element, only one chip capacitor 15 is attached.By using the printed board, for example, at the time of changing fromthe circuit shown in FIG. 2A to the circuit shown in FIG. 2B or FIG. 2C,or to another circuit, the changing can be performed only by changingthe printed board itself where the circuit element is assembled withoutchanging the assembled structure of the case cover at all.

[0025] In FIG. 5, a slant hatching portion shows a winding portion onthe printed board, and the soldering is performed at a black portion. Insoldering parts 17, 18, the soldering is performed with the extensionparts 13 extending upward from the end parts of a pair of brush springs8. Consequently, not only being electrically connected but also theprinted board pressed and held in the concave place limited by thecolumned part formed integrally with the synthetic resin case cover ismechanically surely fixed in the case cover by this soldering.Consequently, the assembling of the case cover itself is finished, andafter that, the step advances to the assembling step of the total of thesmall-sized motor.

[0026] At the time of assembling the small-sized motor, a metal case towhich a magnet is attached, a rotor where the assembly is completed, anda case cover where the assembly is completed are prepared. Then, afterletting one end of the rotor shaft pass through the bearing at the metalcase bottom part, the case cover is fitted to the opening part of themetal case, and after that, not only the soldering part 14 on theprinted board is mechanically connected to the projection in the notchprovided to the case cover to be described later by soldering but alsoit is body-earthed, so that the assembling as the small-sized motor iscompleted.

[0027] This soldering will furthermore be described by referring to FIG.4. FIG. 4 is a view showing the metal case, and FIG. 4D is a view madeby seeing an interior from an opening part of the metal case, and a viewmade by seeing this drawing (FIG. 4D) from the upper side is FIG. 4A,and a view showing that by an upper half cross section seen from theside is FIG. 4C. FIG. 4B is a view showing an expanded projection 10provided on the opening part side of the metal case.

[0028] The projection 10 in the notch 9 provided to the metal case isprovided at such a position where the soldering part 14 on the printedboard comes into contact with this projection 10 when the case cover isfitted to the metal case opening part. At the soldering part 14, solderof a specified amount is already heaped up in advance before fitting thecase cover. The tip of the projection 10 is positioned at a placeretreated from the metal case opening part end surface by an amountapproximately equal to the amount by which the soldering part 14 is madehigher with the heaped solder. As exemplified, two projections 10 areprovided in the notches 9, and furthermore, corresponding thereto, thesoldering parts 14 are provided at four places (refer to FIG. 5), and itis an object of this to make the body-earth and the mechanicalconnection surer, and each one can sufficiently functions. Furthermore,as clearly shown especially in FIG. 4B, in the case of this projection10, the tip side thereof is bent in the metal case interior direction.It is undesirable from the point of view of the beauty that the solderruns over in the outside direction of the case at the time of performingthe soldering to be described later, but by bending the tip side in theinside direction like this, the solder can be prevented from runningover in the outside direction of the case.

[0029] When the case cover is fitted to the metal case opening part, theprojection 10 comes into contact with the soldering part 14 on theprinted board, and even if part thereof bites in, the connection is notcompleted yet in this state. In order to complete this, the solder ismelted by the principle of the electric resistance welding to make thecontact and the connection more stable. This electric resistance weldingis performed by bringing a pair of electrodes for the electricresistance welding into contact with a part where heating is necessary,that is, a place near the projection 10 (refer to FIG. 4A). However, asmentioned above, the electric resistance welding is performed afterfitting the case cover to the metal case. By letting the electriccurrent flow through these electrodes, the heating is performed betweenthe electrodes because of the electric resistance included in the steelmetal case, and the heat thereof is transmitted to the projection 10,and consequently, the solder is melted by the principle of the electricresistance welding, and the welding is performed.

[0030] The present invention makes it possible to easily and surelybody-earth the earth of the electric circuit made of the electricelement such as a chip capacitor attached on a printed board mounted toa case cover, to a metal case.

[0031] Furthermore, the present invention makes it possible to reducethe number of motor assembling steps to perform the assembling with agood workability.

[0032] Furthermore, the projection in the notch can prevent the solderfrom running over in the outside direction of the case by bending thetip side thereof in the metal case interior direction.

What is claimed is:
 1. A small-sized motor, comprising: a hollowcylindrical metal case with a bottom where a magnet is attached to aninside periphery; a synthetic resin case cover which is fitted to closean opening part of said case; and a rotor where a laminated core, awinding wound around said laminated core, and a commutator are attachedon a shaft, wherein to said case cover, a printed board where anelectric circuit including an electric element is attached is mounted,and said printed board has a soldering part which is connected to amember attached to the interior of the case cover for being connected toan electric power source supplied from the outside and a soldering partwhich is connected to a projection in a notch provided on the openingpart side of said metal case for body-earthing the earth of saidelectric circuit, and in said soldering part for the body-earthing, whenassembling the motor, a pair of electrodes are brought into contact fromthe outside of the metal case near said soldering part to weld saidsoldering part by the principle of electric resistance welding, afterfitting said case cover to said metal case opening part.
 2. Thesmall-sized motor according to claim 1, wherein the tip side of saidprojection in the notch is bent in the case interior direction.
 3. Amanufacturing method of a small-sized motor, comprising steps of:inserting a rotor where a laminated core, a winding wound around saidlaminated core, and a commutator are attached on a shaft, into a hollowcylindrical metal case with a bottom where a magnet is attached to aninside periphery; and fitting a synthetic resin case cover to close anopening part of said case, wherein to said case cover, a printed boardwhere an electric circuit including an electric element is attached ismounted, and said printed board has a soldering part which is connectedto a member attached to the interior of the case cover for beingconnected to an electric power source supplied from the outside and asoldering part which is connected to a projection in a notch provided onthe opening part side of said metal case for body-earthing the earth ofsaid electric circuit, and at the time of assembling the motor, afterfitting said case cover to said metal case opening part, a pair ofelectrodes are brought into contact from the outside of the metal casenear said soldering part for the body-earthing to weld said solderingpart by the principle of electric resistance welding.
 4. Themanufacturing method of a small-sized motor according to claim 3,wherein the tip side of said projection in the notch is bent in the caseinterior direction.